Method of conserving fresh fish



Dec. 22, 1964 H. BECKMANN 3,162,020

METHOD OF CONSERVING FRESH FISH Original Filed April 11, 1957 2Sheets-Sheet 1 HM, b 41701 01614! Dec. 22, 1964 H. BECKMANN METHOD OFCONSERVING FRESH FISH Original Filed April ll, 1957 2 Sheets-Sheet 2irrogne Y1 United States Patent sea 3,162,920 METHQD 9F C(BNSERVTNGFRESH FHSH Hans Beclunann, Hamburg, Germany; Erna Marie Dora EmilieEeckmann, Ludwig E. H. K. B. Beclrmanu, and Uta Renate Beclimann, heirsto Hans Eeckmann, deceased Griginal application Apr. 11, 1957, Ser. No.652,139, new Patent No. 2,987,404, dated June 6, 1961. Divided and thisapplication Apr. 12, 1961, Ser. No. 111,886

Claims. (Ci. oil-2%) This invention relates to a process for conservingand cooling foods, more especially fish, and also to apparatus forcarrying such a process into effect. As compared with pickling andsterilisation, the conservation of foods by cooling or refrigeration hasthe advantage that neither the valuable structural substances, enzymes,ferments and vitamins nor the aromatic substances and the naturalcolouring substances of the foods are destroyed. For this reason, therefrigeration processes are preferentially employed for the conservationof foods. This application is a division of application Serial No.652,139, filed April ll, 1957, now Patent No. 2,987,404, dated June 6,1961.

Refrigeration and conservation is of particular importance as regardsfish, since in contrast to the tissues of warm-blooded animals, thetissues of fish are not sterile. They contain large quantities ofseawater bacteria, which in conjunction with the enzymes and fermentsdevelop an intensive decomposition activity immediately after biologicaldeath has occurred. The autolytic processes usually proceed withextraordinary rapidity, because the conditions existing on board shipafter the fish have been caught only differ to a slight degree from theotherwise natural living conditions. Even if the autolysis initiallydoes not produce any harmful decomposition products, it does howevercause the unpleasant and penetrating fish odour due to formation oforganic amines, for example trimethyl amine.

It is true that these phenomena can be effectively counteracted if anintensive refrigeration is carried out immediately after the catch is onboard. However, this is usually not possible, because the extensiveequipment necessary for this purpose cannot be installed on a fishingvessel of present-day size. The fishermen are consequently restricted toadding ice carried on the ship in order that the temperature in the fishhold is at least kept at a tolerable value. The lowering of temperaturewhich is possible by adding ice however, has practically no conservingeffect, because it is hardly lowered to an appreciable degree ascompared with the normal body temperature of the fish of 4-10 C.Moreover, the oxygen which promotes the development of seawater bacteriaand causes the oxidation of the fatty substances has unrestrictedaccess. In addition, pathogenic bacteria find an excellent nutrientmedium in the water from melting ice enriched with albumin.

The deterioration taking place at ever increasing speed as a function oftime makes it necessary that the return journey of the fishing vesselshould be started at the latest 10 days of fishing, so that the fishcaught in the first few days do not completely decay. Owing to the timefactor the loading capacity of the fishing vessel can usually be used toonly 60% of its capacity so that the economy is jeopardised by the highcosts of a fishing trip.

After the catches have been landed, it is true that a refrigeratingtreatment, and usually even a deep-freezing treatment, is carried outwith processed fish which are intended for dispatch, but thesetreatments cannot eliminate the damage which has occurred since the fishwere caught.

In order to obviate these difficulties, a very large number of differentrefrigerating processes have become ice known; for example, the fish onboard a trawler are immediately deep-frozen by means for example of aBirdseye apparatus, in which ammonia evaporating between aluminiumplates is adapted to circulate. In other processes, tightly closed metalcontainers are sprayed with low-cooled salt water or are dipped inliquid air. According to another process, the so-called wind tunnelprocess, the foodstuffs are conducted through a Wind tunnel and theresubjected to very rapid air impulses from pipes cooled to a lowtemperature (-40 to 60 C.) with ammonia.

All these deep-freezing processes have the disadvantage that on the onehand very costly refrigeration units have to be employed and anunnecessary expenditure for equipment is necessary for this purpose.Furthermore, deepfreezing in many cases damages the material to be keptfresh, so that it would be expedient only to cool to such a degree as isabsolutely necessary. The latter is all the more essential, in that thetemperatures, once they are chosen, have to be constantly mantaiued, andthus require the maintenance of the cold conditions until the materialto be kept fresh has reached the consumer. This is im portant, becauseslight changes in temperature with frozen foods lead torecrystallisation processes within the cells and thus in certaincircumstances cause a destruction of the :cell structure.

One object of the invention therefore is to improve the quality ofconserved food especially fish.

A further object of the invention is to bring forth an improved andsimplified method to conserve food especially fish.

Yet another object of the invention is to perform an improved andsimplified method to cool fresh, liquidcontaining food especially fish.

A further object of the invention is to improve and simplify the storageof food especially fish.

Another object of the invention is to improve and simplify the transportor shipment of cooled food especially fish.

A further object of the invention is to produce simple and elfectiveapparatus for cooling food especially fish.

Another object of the invention is to produce simple and effectiveapparatus for storing cooled food especially fish.

The foregoing and other objects of the invention are attained in thesystem illustrated in the accompanying drawings and described below. Itis to be understood that the invention is not limited to the specificform thereof shown and described.

The disadvantages referred to are obviated by the process according tothe invention because the prepared foods (and more especially fish) aresubjected in vacuo to degasification and are thereafter orsimultaneously cooled by utilising the evaporation enthalpy of thenatural body liquid and/or liquid, in that the prepared foods aresubjected to a vacuum in a container which is connected to a suctionpump, it being possible for additional liquid, preferably purified freshor salt Water, to be added prior to, or during, the evacuation bysuction.

Therefore, the considerable heat of evaporation of the water, whichamounts to 583 cal./ g. at room temperature, is used for cooling thefood which is to be kept fresh, in that the evaporation of the water isproduced by apply ing a high vacuum.

Since the heat of evaporation of the water at 0 C. is somwhat greaterthan at room temperature, namely 597 cal./g., an even better effect isobtained when fresh or salt water ice is added to the food to beconserved in the containers. v

A process according to the invention will now be described withreference to the accompanying drawings,

' wherein:

FIG. 1 is an elevation, partly in section, of a fishing vessel which isequipped with the means according to the invention for carrying theprocess into effect.

FIG. 2 is a plan view of a part of the fishing vessel shown in FIG. 1,

FIG. 3 shows a treatment tank with the pump assembly connected theretowhich forms part of the vessel of FIG. 1,

FIG. 4 is a cross-section similar to FIG. 3 of a modified form oftreatment tank,

FIG. 5 is a cross-section through a processing and storage buildingincorporating equipment according to the invention, I

FIG. 6 is a plan view, partly in section, of the building shown in FIG.5, and

FIG. 7 is an enlarged cross-sectional view taken along the line 7-7 ofFIG. 3 and showing the construction of a double-walled tank andvacuum-scalable cover.

The process according to the invention is based on the followingbiological and physical principles: the fish must be killed immediatelyafter being caught, since otherwise the autolytic processes are stronglyassisted by a slow dying process. Furthermore, the treatment accordingto the invention must be carried out before loosening of rig-or mortis,that is to say, Within 46 hours. Furthermore, the fish must be deaeratedand de-gasified, after possibly carrying out the gutting operation. Bythis means, the absorption of those gases which promote thedecomposition process is prevented. Furthermore, there is also removedthereby the oxygen which promotes the development of seawater bacteria,and oxidation processes within the cells areprevented. Furthermore, withthe process according to the invention, the temperature requires to belowered only to such a degree that the body cell contents and theintercellular liquid do not freeze, whereby damage to the tissue due toice crystals is avoided, and finally it is necessary with the presentprocess to cool the fish as far as possible uniformly to about l C. andconstantly to maintain this temperature and prevent further access ofair so that the decomposition processes are prevented or sufiicientlyretarded.

The manner in which the process is carried into effect technically willhereinafter be described in detail. After being caught, the fish areimmediately killed, gutted if necessary and carefully washed. The fishthus prepared are placed in a tank 1, which is preferably of cylindricalconstruction and can be closed in air-tight manner. The fish aresubjected to the treatment according to the invention inside the saidtank.

These vacuum tanks can be made of double-wall con-.

struction (outer wall 21 and inner wall 22 in FIGURE 7) to avoid heatradiations, the space between the inner and outer walls being evacuatedor cooled or provided with an insulating material 23, so that convectionof heat from outside is prevented. It is merely the very small heatquantities occurring due to radiation which are to be intercepted. Withthe temperature difiercnces occurring in practice, these radiations canbe maintainedby suitable measures at about 5 large calories per 'squaremetre per hour. radiations by placing a spiral coil lined with metalfoils around the inner tank (or in the space between the two nestedtanks, the said coil being connected to a refrigerator or very lowcapacity.

In one form of the invention, the tanks have a capacity of 50 tons. Itis however possible for the tanks to be of such dimensions that they canbe hoisted out of the fishing vessel after berthing, if necessary placedon trucks and immediately stored or transported. The tanks can be soarranged in the hold 24 formed by outer skin 25 of the ship that six toeight tanks are juxtap-osedin two rows, the covers 15 of the separatetanks appearing as hatches through the deck 26 which has apertures 27.Covers 15 are vacuum tight-scalable against the tanks by seals 28, seenin FIGURE 7. The tanks are cylindrical,

It is however quite possible to minimise these their upper and lowerwalls being convex as indicated at 29 and 31 respectively in FIGURE 3.

All tanks 1 are connected by way of shut-off valves 3 to a main pipingsystem 2, which leads to a steam jet pump 4. This steam jet pump ispreferably situated in the engine room of the ship and is suppliedthrough the pipes 12 with live or waste steam. By means of this pump thegaseous constituents, mainly air, are evacuated from the tank and thusfrom the bodies of the fish, the vacuum in the tank finally reaching apressure of 2 mm. mercury column.

The tank is provided with a water injection device 5 and can, inaddition, also comprise a pump 6 or a stirrer mechanism 7, these twodevices being provided to prevent the formation of a solid ice crust andin addition increase the flow velocity and thus the heat transfer byconvection.

It is also possible for the vacuum tanks to be so constructed that smallseparate vessels 8, for example wire baskets or trucks (FIG. 4) arearranged in the tanks and can be introduced or removed through anopening 16.

In addition, cooling coils ll? of a refrigeration plant 9 can bearranged in the tank 1.

After a catch has been prepared in the manner indicated above, the cover15 of the vacuum tank 1 is opened and the fish is introduced. Afterclosing the tank and opening the shutoff valve 3 leading to the mainsuction pipe, the tank is connected to the steam jet pump 4. Within ashort time, air and gases are removed from the tank and from the fish bythe pump, so that a very high vacuum is set up.

With a pressure of 2 mm. mercury column, the water adhering to the fishis immediately evaporated at a temperature down to l0 C. Inconsideration of the considerable heat of evaporation or evaporationenthalpy of the water or of the aqueous liquids, the fish is cooled. Athin layer of ice is formed, which is immediately liquefied again by theheat subsequently fiowing from the bodies of the fish, so that theevaporation process can proceed without interruption. By choice of asuitable vacuum, this process can be largely adapted to prevailingconditions. Since the cold is generated directly, i.e. Withoutintermediate carrier, on the body of the fish, there is produced anintensive cooling of the fish within a shortest possible time.

After evaporation of the externally adhering water, which process onlytakes a few minutes, further water is supplied through the water supplyor spray device 5 and the contents of the tank are superficially wetted.The water supplied can be salt or fresh water, but filtered seawater isusually preferred. The evaporation process is continued until the fishhave been cooled down to the required temperature, which is about l C.

In order to simplify the process, the total catch of fish broughtinboardcan also be flooded with seawater. The de-gasification and cooling thenproceeds in exactly the same manner, but now the heat is extracted fromthe fish not directly, but by means of convection. With thissomewhatnsimplified process, it is however necessary to take care that acontinuous area of ice is not formed at the surface. Such a covering ofice would counteract the evaporation of the Water and would thus makethe cooling difiicult. In order to prevent this, the tank ll can beequipped with the stirrer mechanism 7 or the pump 6, so that the liquidis circulated during the treatment. By selecting a predetermined vacuum,any desired degree of coldness can be achieved.

The flooding of the fish with water has the advantage that owing to thebuoyancy, the pressure obtaining inside the heap of fish is largelyreduced, so that pressure zones and damage to the fish to be preservedare avoided.

For further accelerating the process and for increasing the value of theheat of evaporation of the water, it has proved to be advantageous toadd fresh or seawater ice to the fish in the tanks. It has proveddesirable in such cases to add icein an amount of approximately 10% of athe weight of fish. It has also been found to be advantageous in thiscase that the free flow of the water between the fish by means of a pump6 or stirrer mechanism 7 should be assisted by a forced circulation.

A single filling or repeated filling can be carried out, depending onthe size of the tank. For example, large tanks holding 50 tons can becharged four times before they are completely filled. The tanks are thenleft Without any special supervision, except that the temperature andthe vacuum are checked at intervals. The regulation of these variablescan also be effected automatically.

The vacuum tanks 1 can also be made smaller so that it is possible,after the ship has berthed, for the tanks to be lifted out of the shipso as to be set down on trucks, so that they can thereafter be stored ortransported. It is however also possible to use even smaller separatecontainers 8 which can be easily carried by hand. In this case, thetreatment is carried out as follows:

The separate containers 8, which are in the form of wire baskets or ofrectangular vessels which are open at the top, are introduced into alarge vacuum tank 1. After closing the cover 15 or the entrance door 16(FIG. 4), the de-gasification, deaeration and evacuation is carried outin the manner set forth above.

After reaching the vacuum necessary for operational purposes, water isintroduced into the tanks so that the spaces between the fish arefilled. By the strong cooling action, this water is partially orcompletely changed into ice. The evacuation is continued until acontinuous layer 7 of ice has formed on the surface of the separatecontainer 8this layer prevents any access of air. Depending on the sizeof the tank 1 and the vessels 8, and also depending on circumstances,this icing lasts approximately l0 minutes. Thereafter, these separatecontainers 8 can either remain in the vacuum tank 1 or can be stored ina separate fish hold or a larger tank, it being necessary to keep theambient temperature at 1 C. in order to prevent thawing. By this means,the same effect is obtained as in the previous process with large tanks,but the handling operations with the previous processes is somewhatrnore complicated and time-consuming. In contradistinction thereto thefish to be conserved are packed, according to the present invention, insmaller quantities, this being perhaps an advantage on berthing.

The cold vapours formed during evacuation of the tank can be immediatelyextracted through the steam jet pump 4 and deposited in a condenser 11connected on the output side. It is however also possible, and evenadvantageous, for the cold vapours tobe deposited as ice on a coolersituated inside the tank or on cooling coils of a refrigerating plant 9.This method leads to the same result, but with the difference that theice formed on the cooling coils it) can be broken off and falls into thetank 1. By this means, a supplementary ice reserve is provided fortransport purposes and this method is more advantageous from an economicpoint of view.

The fish treated by this process are of first-class quality. Afterlanding, they can be stored and transported in the tanks of the typepreviously described. In the case where a processing stage is provided,for example filleting, deepfreezing or the like, the products are storedand transported in the same tanks, the energy consumption even attemperatures of -20 then being infinitesimally small.

In detail, when the fish are stored with the use of the vacuum tanksaccording to the invention, the process hereinafter described byreference to FIGS. 5 and 6 is employed. The foods, for example fish,arriving in the tanks or also in other ways, we prepared in the groundfloor 18 of a processing and storage building. They are filleted in afilleting machine 24 and thereafter packed at a packing station 25. Thefish the-n reach a deepfreezing apparatus 26, where they are cooled tothe necessary temperature. From the latter, the deep-frozen and fullyprepared and packed fish are stored in vacuum tanks 1. These vacuumtanks for storage purposes are similar to the tanks previouslymentioned, but they are preferably of smaller size, namely 15 tons.

The filled vacuum tanks 1 are closed andconveyed into a storage room 19.For easier manipulation, the tanks 1 are mounted on undercarriages 17,so that they can be brought (while on said undercarriages) to theirstorage position by movement on rails 20 and turntables 21.

It has proved to be desirable that the cellar of building 18 should beused as storage room. In this way, the landed fish are most expedientlyprocessed in a continuous working operation.

The vacuum tanks can be evacuated in the storage room 19 or evendirectly after leaving the deep-freezing station 26. Transportation ofthe tanks from the processing floor 18 to the storage room 1? can beeffected by hoists or lifts 22.

Due to the provision of vacuum storage tanks which are of double-walledconstruction, there is no longer any appreciable exchange of heatbetween the cooled fish and the outside air. In order to compensate forany heat losses which may occur, it is possible to provide thepreviously mentioned refrigerating plants 9 on the storage tank 1. Thefish in these vacuum tanks can be stored for relatively long periods oftime.

The transport of the fish from the processing and storage building tothe wholesaler is preferably also carried out in these vacuum tanks 1.For this reason, the tanks are of such dimensions that they can beloaded Without any difficulty on railway trucks 23 or other means oftransport. When using tanks with a capacity of approximately l5 tons, 3of these tanks can, for example, be conveniently arranged on one truck.If it is desired that the fish in the tank should be further cooledwhile it is being transported, the refrigerating plant 9 can for examplebe supplied by a small generator which i arranged on the axles of thetruck.

By using such vacuum tanks, it is possible to dispense with the use ofspecial refrigerator trucks, and in addition the previous storage of thedeep-frozen material, as previously mentioned, can now also take placein the cellars of warehouses. This storage in cellars could not hithertoalways be carried out, since the storage of deepfrozen articles thereinor the low cooling of the cellar itself could only be achieved withheavy expense for insulating material. If such a cellar, usually a dampcellar, is used as refrigeration room, damage to the concrete wall ofthe cellar occurs in a comparatively short time, the moisture in thecellar wall causes the latter to crack due to freezing.

The present process operates with less initial outlay and in aconsiderably more economic manner than the prior known processes and isof particular importance for use in tropical zones.

Owing to the better quality of the fish, a substantially higher profitis made from the catch and the loading capacity of the ships, whichhithereto could generally be utilised only to 60% capacity is increasedto 10()% owing to the fact that the ships can remain for a longer periodin the fishing zone and to the saving of storage space, the latterbecause the carrying of ice can be completely dispensed with or veryconsiderably restricted.

It is obvious that the process which has been described can be used inconnection with other foods, which are to be de-gasified and cooled in acorresponding manner for conservation purposes.

What I claim is: v

1. A fishing vessel comprising an outer skin and a deck defining a hold,the deck having a plurality of apertures, an equal plurality of tankswithin said hold, each of said tanks having an opening at its top and acover lid, said opening being vacuum tight-scalable by means of saidcoverlid, said openings of said tanks registering with the apertures inthe deck and being thereby accessible, a piping system and vacuumpumping means connected to said piping system, each of said tanks beingprovided with a connection pipe at its upper part, a shut-01f valvebeing disposed in said connection pipe, by means of which each of saidtanks is disconnectably connected to said piping system, and a watersupply system, each of the tanks being connected to said water supplysystem at the top of the tank.

2. A fishing vessel comprising an outer skin and a deck defining a hold,the deck having a plurality of apertures, an equal plurality of tanksWithin said hold, each of said tanks having an opening at its top and acover lid, said opening being vacuum tight-scalable by means of saidcover lid, each of said openings of said tanks being re ceived within arespective one of said apertures and being thereby accessible, a pipingsystem, and vacuum pumping means connected to said piping system, eachof said tanks being provided with a connection pipe at its upper part, ashut-off valve being disposed in said connection pipe by means of whicheach of said tanks is disconnectably connected to said piping system, aWater supply system being connected to each of said tanks forvoluntarily supplying Water thereto, means for agitating water beinglocated within each of said tanks.

3. A fishing vessel comprising a deck, a plurality of apertures beingprovided in that deck, an equal plurality of single walled tanks beingdisposed under said deck, each tank having an opening at its top and acover lid, said opening being received in a respective one of saidapertures and being vacuum tight-scalable by means of said cover lid,each of said tanks being surrounded by a second wall, thereby definingan outer space, a piping system, and vacuum pumping means connected tosaid piping system, each of said tanks being provided with a connectionpipe at its upper part, a shut-off valve being disposed in saidconnection pipe by means of which each of said tanks is disconnectablyconnected to said piping system, a water supply system being connectedto each of said tanks for selectively supplying water thereto, means foragitating water being located Within each of said tanks.

4. A fishing vessel comprising a deck, a plurality of apertures beingprovided in said deck, an equal plurality of tanks being disposed undersaid deck and in registration with said apertures, each tank havingatleast one opening and a cover lid, said opening being vacuumtightsealable by means of said cover lid, a plurality of separatecontainers of predetermined lateral dimensions disposed Within said tankalongside each other, the dimensions of said opening being such as topermit the passage of said separate containers therethrough, spray meansat the top of each tank capable of inserting a sufficient amount ofwater to immerse the food contained therein, a piping systern, andvacuum pumping means connected to said piping system, each of said tanksbeing provided with a connection pipe at its upper part, a shut-offvalve being disposed in said connection pipe, by means of which each ofsaid tanks is disconnectably connected to said piping system.

S. In a container for de-gasifying and cooling fresh, liquid-containingfood, especially fish, a housing with convex walls capable ofwithstanding a very high degree of internal vacuum, said housing havingan inner housing and an outer housing, said outer housing encompassingsaid inner housing for forming a closable intermediate space, heatinsulating means provided within said intermediate space, a vacuum pumpof relatively high suction power, means for connecting said vacuum pumpwith said container, means within the interior of said container foragitating its contents only sufiiciently to prevent the formation of acomplete ice layer due to slow heat transfer, spray means located at thetop of said container capable of inserting a suflicient amount of Waterinto said container to immerse the food contained therein, a detachableconvex-shaped cover adapted to fit over an aperture in the upper part ofsaid container, and means for sealing said cover against said containerwhen placed over said aperture.

Reierences Qited by the Examiner UNlTED STATES PATENTS ROBERT A. OLEARY,Primary Examiner.

HYMAN LORD, Examiner.

1. A FISHING VESSEL COMPRISING AN OUTER SKIN AND A DECK DEFINING A HOLD,THE DECK HAVING A PLURALITY OF APERTURES, AN EQUAL PLURALITY OF TANKSWITHIN SAID HOLD, EACH OF SAID TANKS HAVING AN OPENING AT ITS TOP AND ACOVER LID, SAID OPENING BEING VACUUM TIGHT-SEALABLE BY MEANS OF SAIDCOVER LID, SAID OPENINGS OF SAID TANKS REGISTERING WITH THE APERTURES INTHE DECK AND BEING THEREBY ACCESSIBLE, A PIPING SYSTEM AND VACUUMPUMPING MEANS CONNECTED TO SAID PIPING SYSTEM, EACH OF SAID TANKS BEINGPROVIDED WITH A CONNECTION PIPE AT ITS UPPER PART, A SHUT-OFF VALVEBEING DISPOSED IN SAID CONNECTION PIPE, BY MEANS OF WHICH EACH OF SAIDTANKS IS DISCONNECTABLY CONNECTED TO SAID PIPING SYSTEM, AND A WATERSUPPLY SYSTEM, EACH OF THE TANKS BEING CONNECTED TO SAID WATER SUPPLYSYSTEM AT THE TOP OF THE TANK.